/*
 * Copyright (c) 1982, 1986, 1989, 1990, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by the University of
 *	California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *	@(#)uipc_syscalls.c	8.4 (Berkeley) 2/21/94
 */

#include <sys/param.h>
#include <sys/filedesc.h>
#include <sys/proc.h>
#include <sys/file.h>
#include <sys/buf.h>
#include <sys/malloc.h>
#include <sys/mbuf.h>
#include <sys/protosw.h>
#include <sys/socket.h>
#include <sys/socketvar.h>
#ifdef KTRACE
#include <sys/ktrace.h>
#endif

/*
 * System call interface to the socket abstraction.
 */
#if defined(COMPAT_43) || defined(COMPAT_SUNOS)
#define COMPAT_OLDSOCK
#endif

extern	struct fileops socketops;

/*
	函数功能: 返回一个文件描述符，用于网络通信后续使用

	内部实现: 把进程结构-文件描述符表-协议控制块联系起来；把socket与协议关联起来	
	
	调用举例:
	fd_s = socket(AF_INET, SOCK_RAW, IPPROTO_ICMP);
	fd_s = socket(AF_INET, SOCK_STREAM, 0 );
*/
struct socket_args {
	int	domain;
	int	type;
	int	protocol;
};
socket(p, uap, retval)
	struct proc *p;
	register struct socket_args *uap;
	int *retval;
{
	struct filedesc *fdp = p->p_fd;
	struct socket *so;
	struct file *fp;
	int fd, error;

	if (error = falloc(p, &fp, &fd))
		return (error);
	fp->f_flag = FREAD|FWRITE;
	fp->f_type = DTYPE_SOCKET;
	fp->f_ops = &socketops;
	if (error = socreate(uap->domain, &so, uap->type, uap->protocol)) {
		fdp->fd_ofiles[fd] = 0;
		ffree(fp);
	} else {
		fp->f_data = (caddr_t)so;	/* 把socreate新创建的socket与文件描述符绑定 */
		*retval = fd;				/* 把为socket创建的文件描述符传出，返回给调用socket()的进程 */
	}
	return (error);
}

/*
	函数功能: 把网络层地址、端口号与socket关联起来，可以标识本地进程

	内部实现: 检查网络层地址有效性，并把协议族(AF_INET)、网络层地址和端口号填入协议控制块
	
	调用举例:
	struct sockaddr_in server_addr;
	
	memset(&server_addr, 0, sizeof(server_addr)) ;
    server_addr.sin_len = sizeof(addr);
	server_addr.sin_family = AF_INET;
    server_addr.sin_addr.s_addr = 本地可用ip地址;
    server_addr.sin_port = 非0端口号;

    bind(fd_s, (struct sockaddr *)&server_addr, sizeof(server_addr)) ;
*/
struct bind_args {
	int	s;
	caddr_t	name;
	int	namelen;
};
/* ARGSUSED */
bind(p, uap, retval)
	struct proc *p;
	register struct bind_args *uap;
	int *retval;
{
	struct file *fp;
	struct mbuf *nam;
	int error;

	if (error = getsock(p->p_fd, uap->s, &fp))
		return (error);
	if (error = sockargs(&nam, uap->name, uap->namelen, MT_SONAME))
		return (error);
	error = sobind((struct socket *)fp->f_data, nam);
	m_freem(nam);	/* 释放在上面(sockargs函数)分配的mbuf */
	return (error);
}

/*
	函数功能: 准备接受tcp连接，并限制连接数

	内部实现: 设置tcp状态为TCPS_LISTEN监听
	
	调用举例:
    listen(fd_s, 5);
*/
struct listen_args {
	int	s;
	int	backlog;
};
/* ARGSUSED */
listen(p, uap, retval)
	struct proc *p;
	register struct listen_args *uap;
	int *retval;
{
	struct file *fp;
	int error;

	if (error = getsock(p->p_fd, uap->s, &fp))
		return (error);
	return (solisten((struct socket *)fp->f_data, uap->backlog));
}

/*
	函数功能: 等待tcp连接请求，获得客户端ip和端口信息并返回该tcp连接socket

	内部实现: 当监听socket维护的已建立连接队列非空时，从此队列获取一个tcp连接，该tcp连接以另一个socket(client_socket)的形式存在
			  从client_socket的协议控制块中，获取客户端协议族(AF_INET)、网络层地址和端口号，并把client_socket与文件描述符表关联起来
			  client_socket用于当前tcp连接的数据处理，监听socket准备接收下一个连接
	
	调用举例:
	struct sockaddr client_addr;	
	int size = sizeof(struct sockaddr);
	
    fd_c = accept(fd_s, &client_addr, &size);
*/
struct accept_args {
	int	s;
	caddr_t	name;
	int	*anamelen;
#ifdef COMPAT_OLDSOCK
	int	compat_43;	/* pseudo */
#endif
};

#ifdef COMPAT_OLDSOCK
accept(p, uap, retval)
	struct proc *p;
	struct accept_args *uap;
	int *retval;
{

	uap->compat_43 = 0;
	return (accept1(p, uap, retval));
}

oaccept(p, uap, retval)
	struct proc *p;
	struct accept_args *uap;
	int *retval;
{

	uap->compat_43 = 1;
	return (accept1(p, uap, retval));
}
#else /* COMPAT_OLDSOCK */

#define	accept1	accept
#endif

accept1(p, uap, retval)
	struct proc *p;
	register struct accept_args *uap;
	int *retval;
{
	struct file *fp;
	struct mbuf *nam;
	int namelen, error, s;
	register struct socket *so;

	/* 在此将进程传入缓存长度anamelen赋给内核临时变量namelen，在该函数退出时，再反向操作。这个行为很迷惑，猜测可能是保护数据。 */
	if (uap->name && (error = copyin((caddr_t)uap->anamelen,
	    (caddr_t)&namelen, sizeof (namelen))))
		return (error);


	/* 从文件描述符表获得了监听socket */
	if (error = getsock(p->p_fd, uap->s, &fp))
		return (error);
	s = splnet();
	so = (struct socket *)fp->f_data;
	if ((so->so_options & SO_ACCEPTCONN) == 0) {
		splx(s);
		return (EINVAL);
	}

	if ((so->so_state & SS_NBIO) && so->so_qlen == 0) {	/* 当监听socket维护的已建立连接队列为空 且 设置了进程不阻塞时，立即返回 */
		splx(s);
		return (EWOULDBLOCK);
	}


	/* 协议处理层通过设置 so_error 设置差错码或唤醒等待在socket上的所有进程，来通知socket状态的改变 */
	while (so->so_qlen == 0 && so->so_error == 0) {
		if (so->so_state & SS_CANTRCVMORE) {				/* 监听socket不再接收对端数据时，不再等待tcp连接到来 */
			so->so_error = ECONNABORTED;
			break;
		}
		/* 当协议层通过sonewconn将一条连接插入队列后，唤醒等待的进程。 */
		if (error = tsleep((caddr_t)&so->so_timeo, PSOCK | PCATCH,	/* 接收到一个有差错连接、被信号中断或等待超时时，不再等待连接到来 */
		    netcon, 0)) {
			splx(s);
			return (error);
		}
	}
	if (so->so_error) {			/* 检查是否在进程睡眠期间有差错出现 */
		error = so->so_error;
		so->so_error = 0;
		splx(s);
		return (error);
	}


	/* 从监听socket维护的已建立连接队列中移出一个tcp连接，表现为另一个socket(在调用sonewconn时建立)，并把该socket与文件描述符表管理起来 */
	if (error = falloc(p, &fp, retval)) {
		splx(s);
		return (error);
	}
	{ struct socket *aso = so->so_q;
	  if (soqremque(aso, 1) == 0)
		panic("accept");
	  so = aso;
	}
	fp->f_type = DTYPE_SOCKET;
	fp->f_flag = FREAD|FWRITE;
	fp->f_ops = &socketops;
	fp->f_data = (caddr_t)so;


	/* 从已建立连接队列中获取的tcp连接，协议控制块中获取连接信息(客户端协议族(AF_INET)、网络层地址和端口号)并拷贝到进程的缓存中 */
	nam = m_get(M_WAIT, MT_SONAME);
	(void) soaccept(so, nam);
	if (uap->name) {
#ifdef COMPAT_OLDSOCK
		if (uap->compat_43)
			mtod(nam, struct osockaddr *)->sa_family =
			    mtod(nam, struct sockaddr *)->sa_family;
#endif
		if (namelen > nam->m_len)
			namelen = nam->m_len;
		/* SHOULD COPY OUT A CHAIN HERE */
		if ((error = copyout(mtod(nam, caddr_t), (caddr_t)uap->name,
		    (u_int)namelen)) == 0)
			error = copyout((caddr_t)&namelen,
			    (caddr_t)uap->anamelen, sizeof (*uap->anamelen));
	}
	m_freem(nam);
	splx(s);
	return (error);
}

/*
	函数功能: 把网络层地址、端口号与socket关联起来，可以标识本地进程，发出连接请求(在tcp中)

	内部实现: 把检查网络层地址有效性，并把协议族(AF_INET)、网络层地址和端口号填入协议控制块

	调用举例:
	struct sockaddr server_addr;
	struct sockaddr_in *servaddr;

	servaddr = (struct sockaddr_in *)&server_addr;
    servaddr->sin_len = sizeof(*servaddr);
	servaddr->sin_family = AF_INET;
	servaddr->sin_port = htons(服务端bind绑定的端口号);
    servaddr->sin_addr.s_addr = 服务端bind绑定的IP地址;

	fd_c = socket(AF_INET, SOCK_STREAM, 0 );
    connect(fd_c, &server_addr, sizeof(server_addr));

    切断无连接socket插口和外部地址的关联：
	对于无连接协议，可以通过调用 connect，并传入一个不正确的name参数，如指向内容为全0的结构指针或大小不对的结构，来丢弃同socket插口相关联的外部地址。
	sodisconnect删除同socket相关联的外部地址， PRU_CONNECT返回差错代码，如 EAFNOSUPPORT或EADDRNOTAVAIL，留下没有外部地址的插口。
	这种方式虽然有点晦涩，但却是一种比较有用的断连方式，在无连接插口和外部地址之间断连，而不是替换。
*/
struct connect_args {
	int	s;
	caddr_t	name;
	int	namelen;
};
/* ARGSUSED */
connect(p, uap, retval)
	struct proc *p;
	register struct connect_args *uap;
	int *retval;
{
	struct file *fp;
	register struct socket *so;
	struct mbuf *nam;
	int error, s;

	if (error = getsock(p->p_fd, uap->s, &fp))
		return (error);
	so = (struct socket *)fp->f_data;
	if ((so->so_state & SS_NBIO) && (so->so_state & SS_ISCONNECTING))	/* 已有连接请求在非阻塞的插口上 */
		return (EALREADY);
	if (error = sockargs(&nam, uap->name, uap->namelen, MT_SONAME))
		return (error);
	error = soconnect(so, nam);
	if (error)
		goto bad;

	/* 如果 soconnect 返回时连接还没有完成且使能了非阻塞的 I/O，则立即返回EINPROGRESS以免等待连接完成。
	  因为通常情况下，建立连接要涉及同远程系统交换几个分组，因而这个过程可能需要一些时间才能完成。
	  如果连接没完成，则下次对 connect调用就返回EALREADY。当连接完成时，soconnect返回EISCONN */
	if ((so->so_state & SS_NBIO) && (so->so_state & SS_ISCONNECTING)) {
		m_freem(nam);
		return (EINPROGRESS);
	}

	/* 只有socket未设置阻塞标志SS_NBIO，才可能执行下面while语句 */

	/* splnet防止connect在测试插口状态和调用tsleep之间错过wakeup。*/
	s = splnet();
	while ((so->so_state & SS_ISCONNECTING) && so->so_error == 0) 	/* while循环直到连接已建立或出现差错时才退出。*/
		if (error = tsleep((caddr_t)&so->so_timeo, PSOCK | PCATCH,
		    netcon, 0))
			break;
	if (error == 0) {
		error = so->so_error;
		so->so_error = 0;
	}
	splx(s);
bad:	/* 不管连接已完成或失败，都需要释放sockargs时，分配的临时变量 */
	so->so_state &= ~SS_ISCONNECTING;
	m_freem(nam);
	if (error == ERESTART)
		error = EINTR;
	return (error);
}

struct socketpair_args {
	int	domain;
	int	type;
	int	protocol;
	int	*rsv;
};
socketpair(p, uap, retval)
	struct proc *p;
	register struct socketpair_args *uap;
	int retval[];
{
	register struct filedesc *fdp = p->p_fd;
	struct file *fp1, *fp2;
	struct socket *so1, *so2;
	int fd, error, sv[2];

	if (error = socreate(uap->domain, &so1, uap->type, uap->protocol))
		return (error);
	if (error = socreate(uap->domain, &so2, uap->type, uap->protocol))
		goto free1;
	if (error = falloc(p, &fp1, &fd))
		goto free2;
	sv[0] = fd;
	fp1->f_flag = FREAD|FWRITE;
	fp1->f_type = DTYPE_SOCKET;
	fp1->f_ops = &socketops;
	fp1->f_data = (caddr_t)so1;
	if (error = falloc(p, &fp2, &fd))
		goto free3;
	fp2->f_flag = FREAD|FWRITE;
	fp2->f_type = DTYPE_SOCKET;
	fp2->f_ops = &socketops;
	fp2->f_data = (caddr_t)so2;
	sv[1] = fd;
	if (error = soconnect2(so1, so2))
		goto free4;
	if (uap->type == SOCK_DGRAM) {
		/*
		 * Datagram socket connection is asymmetric.
		 */
		 if (error = soconnect2(so2, so1))
			goto free4;
	}
	error = copyout((caddr_t)sv, (caddr_t)uap->rsv, 2 * sizeof (int));
	retval[0] = sv[0];		/* XXX ??? */
	retval[1] = sv[1];		/* XXX ??? */
	return (error);
free4:
	ffree(fp2);
	fdp->fd_ofiles[sv[1]] = 0;
free3:
	ffree(fp1);
	fdp->fd_ofiles[sv[0]] = 0;
free2:
	(void)soclose(so2);
free1:
	(void)soclose(so1);
	return (error);
}

/*
	函数功能: 为sosend准备数据及指定发送地址

	调用举例:
	int len = 10;
	char buffer[20] = {0};
	struct sockaddr server_addr;
	struct sockaddr_in *servaddr;
	int	bytes_sent;

	servaddr = (struct sockaddr_in *)&server_addr;
    servaddr->sin_len = sizeof(*servaddr);
	servaddr->sin_family = AF_INET;
	servaddr->sin_port = htons(服务端bind绑定的端口号);
    servaddr->sin_addr.s_addr = 服务端bind绑定的IP地址;

	bytes_sent = sendto(sockefd, buffer, len, 0, &server, sizeof(server));
*/
struct sendto_args {
	int	s;
	caddr_t	buf;
	size_t	len;
	int	flags;
	caddr_t	to;
	int	tolen;
};
sendto(p, uap, retval)
	struct proc *p;
	register struct sendto_args *uap;
	int *retval;	/* 以发送的数据长度，以系统调用返回值的形式体现 */
{
	struct msghdr msg;
	struct iovec aiov;

	msg.msg_name = uap->to;
	msg.msg_namelen = uap->tolen;
	msg.msg_iov = &aiov;
	msg.msg_iovlen = 1;
	msg.msg_control = 0;
#ifdef COMPAT_OLDSOCK
	msg.msg_flags = 0;
#endif
	aiov.iov_base = uap->buf;
	aiov.iov_len = uap->len;
	return (sendit(p, uap->s, &msg, uap->flags, retval));
}

#ifdef COMPAT_OLDSOCK
struct osend_args {
	int	s;
	caddr_t	buf;
	int	len;
	int	flags;
};
osend(p, uap, retval)
	struct proc *p;
	register struct osend_args *uap;
	int *retval;
{
	struct msghdr msg;
	struct iovec aiov;

	msg.msg_name = 0;
	msg.msg_namelen = 0;
	msg.msg_iov = &aiov;
	msg.msg_iovlen = 1;
	aiov.iov_base = uap->buf;
	aiov.iov_len = uap->len;
	msg.msg_control = 0;
	msg.msg_flags = 0;
	return (sendit(p, uap->s, &msg, uap->flags, retval));
}

#define MSG_COMPAT	0x8000
struct osendmsg_args {
	int	s;
	caddr_t	msg;
	int	flags;
};
osendmsg(p, uap, retval)
	struct proc *p;
	register struct osendmsg_args *uap;
	int *retval;
{
	struct msghdr msg;
	struct iovec aiov[UIO_SMALLIOV], *iov;
	int error;

	if (error = copyin(uap->msg, (caddr_t)&msg, sizeof (struct omsghdr)))
		return (error);
	if ((u_int)msg.msg_iovlen >= UIO_SMALLIOV) {
		if ((u_int)msg.msg_iovlen >= UIO_MAXIOV)
			return (EMSGSIZE);
		MALLOC(iov, struct iovec *,
		      sizeof(struct iovec) * (u_int)msg.msg_iovlen, M_IOV, 
		      M_WAITOK);
	} else
		iov = aiov;
	if (error = copyin((caddr_t)msg.msg_iov, (caddr_t)iov,
	    (unsigned)(msg.msg_iovlen * sizeof (struct iovec))))
		goto done;
	msg.msg_flags = MSG_COMPAT;
	msg.msg_iov = iov;
	error = sendit(p, uap->s, &msg, uap->flags, retval);
done:
	if (iov != aiov)
		FREE(iov, M_IOV);
	return (error);
}
#endif

/*
	函数功能: 为sosend准备数据及指定发送地址
	相较于sendto，sendmsg可以接收来自多个缓存的数据，只要把各个缓存的起始地址和长度放入struct msghdr->msg_iov数组中，调用一次sendmsg即可 
	相较于sendto，应用调用sendmsg系统调用时，需要自己构造struct msghdr结构
*/
struct sendmsg_args {
	int	s;
	caddr_t	msg;
	int	flags;
};
sendmsg(p, uap, retval)
	struct proc *p;
	register struct sendmsg_args *uap;
	int *retval;
{
	struct msghdr msg;
	struct iovec aiov[UIO_SMALLIOV], *iov;
	int error;

	if (error = copyin(uap->msg, (caddr_t)&msg, sizeof (msg)))	/* 从外部空间考取msg到内核，失败退出 */
		return (error);
	if ((u_int)msg.msg_iovlen >= UIO_SMALLIOV) {	/* msg_iov数组中元素个数 >= UIO_SMALLIOV 且 < UIO_MAXIOV时，分配新内存 */
		if ((u_int)msg.msg_iovlen >= UIO_MAXIOV)
			return (EMSGSIZE);
		MALLOC(iov, struct iovec *,
		       sizeof(struct iovec) * (u_int)msg.msg_iovlen, M_IOV,
		       M_WAITOK);
	} else											/* msg_iov数组中元素个数 < UIO_SMALLIOV时，使用数组aiov */
		iov = aiov;
	if (msg.msg_iovlen &&
	    (error = copyin((caddr_t)msg.msg_iov, (caddr_t)iov,
	    (unsigned)(msg.msg_iovlen * sizeof (struct iovec)))))	/* 从外部空间考取msg_iov数组到内核，失败退出 */
		goto done;
	msg.msg_iov = iov;
#ifdef COMPAT_OLDSOCK
	msg.msg_flags = 0;
#endif
	error = sendit(p, uap->s, &msg, uap->flags, retval);
done:
	if (iov != aiov)
		FREE(iov, M_IOV);
	return (error);
}

/* 函数功能: 把调用传来的msghdr结构，拆分为数据信息、地址信息和控制信息(如果存在的话)，调用sosend做准备 */
sendit(p, s, mp, flags, retsize)
	register struct proc *p;
	int s;
	register struct msghdr *mp;
	int flags, *retsize;
{
	struct file *fp;
	struct uio auio;
	register struct iovec *iov;
	register int i;
	struct mbuf *to, *control;
	int len, error;
#ifdef KTRACE
	struct iovec *ktriov = NULL;
#endif
	
	if (error = getsock(p->p_fd, s, &fp))
		return (error);

	/* auio存储要发送的数据信息 */
	auio.uio_iov = mp->msg_iov;
	auio.uio_iovcnt = mp->msg_iovlen;
	auio.uio_segflg = UIO_USERSPACE;
	auio.uio_rw = UIO_WRITE;
	auio.uio_procp = p;
	auio.uio_offset = 0;			/* XXX */
	auio.uio_resid = 0;
	iov = mp->msg_iov;
	for (i = 0; i < mp->msg_iovlen; i++, iov++) {
		if (iov->iov_len < 0)	/* 用户传入的某个缓存长度小于0，直接退出，不再发送 */
			return (EINVAL);
		if ((auio.uio_resid += iov->iov_len) < 0)
			return (EINVAL);
	}

	/* to存储目的地址信息 */
	if (mp->msg_name) {
		if (error = sockargs(&to, mp->msg_name, mp->msg_namelen,
		    MT_SONAME))
			return (error);
	} else
		to = 0;

	/* control存储控制信息 */
	if (mp->msg_control) {
		if (mp->msg_controllen < sizeof(struct cmsghdr)
#ifdef COMPAT_OLDSOCK
		    && mp->msg_flags != MSG_COMPAT
#endif
		) {
			error = EINVAL;
			goto bad;
		}
		if (error = sockargs(&control, mp->msg_control,
		    mp->msg_controllen, MT_CONTROL))
			goto bad;
#ifdef COMPAT_OLDSOCK
		if (mp->msg_flags == MSG_COMPAT) {
			register struct cmsghdr *cm;

			M_PREPEND(control, sizeof(*cm), M_WAIT);
			if (control == 0) {
				error = ENOBUFS;
				goto bad;
			} else {
				cm = mtod(control, struct cmsghdr *);
				cm->cmsg_len = control->m_len;
				cm->cmsg_level = SOL_SOCKET;
				cm->cmsg_type = SCM_RIGHTS;
			}
		}
#endif
	} else
		control = 0;
#ifdef KTRACE
	if (KTRPOINT(p, KTR_GENIO)) {
		int iovlen = auio.uio_iovcnt * sizeof (struct iovec);

		MALLOC(ktriov, struct iovec *, iovlen, M_TEMP, M_WAITOK);
		bcopy((caddr_t)auio.uio_iov, (caddr_t)ktriov, iovlen);
	}
#endif
	len = auio.uio_resid;	/* 因为sosend中会修改总数据长度auio.uio_resid，在此先暂存起来 */
	if (error = sosend((struct socket *)fp->f_data, to, &auio,
	    (struct mbuf *)0, control, flags)) {
	    /* 如果sosend传送了部分数据后，传送被信号或阻塞条件所中断，忽略该差错，给用户返回已传送的数据。 */
		if (auio.uio_resid != len && (error == ERESTART ||
		    error == EINTR || error == EWOULDBLOCK))
			error = 0;

		/* 如果sosend返回EPIPE，发送信号SIGPIPE给进程。 */
		if (error == EPIPE)
			psignal(p, SIGPIPE);
	}
	if (error == 0)
		*retsize = len - auio.uio_resid;	/* 计算已发送的数据长度 */
#ifdef KTRACE
	if (ktriov != NULL) {
		if (error == 0)
			ktrgenio(p->p_tracep, s, UIO_WRITE,
				ktriov, *retsize, error);
		FREE(ktriov, M_TEMP);
	}
#endif
bad:
	if (to)
		m_freem(to);
	return (error);
}

struct recvfrom_args {
	int	s;
	caddr_t	buf;
	size_t	len;
	int	flags;
	caddr_t	from;
	int	*fromlenaddr;
};

#ifdef COMPAT_OLDSOCK
orecvfrom(p, uap, retval)
	struct proc *p;
	struct recvfrom_args *uap;
	int *retval;
{

	uap->flags |= MSG_COMPAT;
	return (recvfrom(p, uap, retval));
}
#endif

recvfrom(p, uap, retval)
	struct proc *p;
	register struct recvfrom_args *uap;
	int *retval;
{
	struct msghdr msg;
	struct iovec aiov;
	int error;

	if (uap->fromlenaddr) {
		if (error = copyin((caddr_t)uap->fromlenaddr,
		    (caddr_t)&msg.msg_namelen, sizeof (msg.msg_namelen)))
			return (error);
	} else
		msg.msg_namelen = 0;
	msg.msg_name = uap->from;
	msg.msg_iov = &aiov;
	msg.msg_iovlen = 1;
	aiov.iov_base = uap->buf;
	aiov.iov_len = uap->len;
	msg.msg_control = 0;
	msg.msg_flags = uap->flags;
	return (recvit(p, uap->s, &msg, (caddr_t)uap->fromlenaddr, retval));
}

#ifdef COMPAT_OLDSOCK
struct orecv_args {
	int	s;
	caddr_t	buf;
	int	len;
	int	flags;
};
orecv(p, uap, retval)
	struct proc *p;
	register struct orecv_args *uap;
	int *retval;
{
	struct msghdr msg;
	struct iovec aiov;

	msg.msg_name = 0;
	msg.msg_namelen = 0;
	msg.msg_iov = &aiov;
	msg.msg_iovlen = 1;
	aiov.iov_base = uap->buf;
	aiov.iov_len = uap->len;
	msg.msg_control = 0;
	msg.msg_flags = uap->flags;
	return (recvit(p, uap->s, &msg, (caddr_t)0, retval));
}

/*
 * Old recvmsg.  This code takes advantage of the fact that the old msghdr
 * overlays the new one, missing only the flags, and with the (old) access
 * rights where the control fields are now.
 */
struct orecvmsg_args {
	int	s;
	struct	omsghdr *msg;
	int	flags;
};
orecvmsg(p, uap, retval)
	struct proc *p;
	register struct orecvmsg_args *uap;
	int *retval;
{
	struct msghdr msg;
	struct iovec aiov[UIO_SMALLIOV], *iov;
	int error;

	if (error = copyin((caddr_t)uap->msg, (caddr_t)&msg,
	    sizeof (struct omsghdr)))
		return (error);
	if ((u_int)msg.msg_iovlen >= UIO_SMALLIOV) {
		if ((u_int)msg.msg_iovlen >= UIO_MAXIOV)
			return (EMSGSIZE);
		MALLOC(iov, struct iovec *,
		      sizeof(struct iovec) * (u_int)msg.msg_iovlen, M_IOV,
		      M_WAITOK);
	} else
		iov = aiov;
	msg.msg_flags = uap->flags | MSG_COMPAT;
	if (error = copyin((caddr_t)msg.msg_iov, (caddr_t)iov,
	    (unsigned)(msg.msg_iovlen * sizeof (struct iovec))))
		goto done;
	msg.msg_iov = iov;
	error = recvit(p, uap->s, &msg, (caddr_t)&uap->msg->msg_namelen, retval);

	if (msg.msg_controllen && error == 0)
		error = copyout((caddr_t)&msg.msg_controllen,
		    (caddr_t)&uap->msg->msg_accrightslen, sizeof (int));
done:
	if (iov != aiov)
		FREE(iov, M_IOV);
	return (error);
}
#endif

struct recvmsg_args {
	int	s;
	struct	msghdr *msg;
	int	flags;
};
recvmsg(p, uap, retval)
	struct proc *p;
	register struct recvmsg_args *uap;
	int *retval;
{
	struct msghdr msg;
	struct iovec aiov[UIO_SMALLIOV], *uiov, *iov;
	register int error;

	if (error = copyin((caddr_t)uap->msg, (caddr_t)&msg, sizeof (msg)))
		return (error);
	if ((u_int)msg.msg_iovlen >= UIO_SMALLIOV) {
		if ((u_int)msg.msg_iovlen >= UIO_MAXIOV)
			return (EMSGSIZE);
		MALLOC(iov, struct iovec *,
		       sizeof(struct iovec) * (u_int)msg.msg_iovlen, M_IOV,
		       M_WAITOK);
	} else
		iov = aiov;
#ifdef COMPAT_OLDSOCK
	msg.msg_flags = uap->flags &~ MSG_COMPAT;
#else
	msg.msg_flags = uap->flags;
#endif
	uiov = msg.msg_iov;
	msg.msg_iov = iov;
	if (error = copyin((caddr_t)uiov, (caddr_t)iov,
	    (unsigned)(msg.msg_iovlen * sizeof (struct iovec))))
		goto done;
	if ((error = recvit(p, uap->s, &msg, (caddr_t)0, retval)) == 0) {
		msg.msg_iov = uiov;
		error = copyout((caddr_t)&msg, (caddr_t)uap->msg, sizeof(msg));
	}
done:
	if (iov != aiov)
		FREE(iov, M_IOV);
	return (error);
}

recvit(p, s, mp, namelenp, retsize)
	register struct proc *p;
	int s;
	register struct msghdr *mp;
	caddr_t namelenp;
	int *retsize;
{
	struct file *fp;
	struct uio auio;
	register struct iovec *iov;
	register int i;
	int len, error;
	struct mbuf *from = 0, *control = 0;
#ifdef KTRACE
	struct iovec *ktriov = NULL;
#endif
	
	if (error = getsock(p->p_fd, s, &fp))
		return (error);
	auio.uio_iov = mp->msg_iov;
	auio.uio_iovcnt = mp->msg_iovlen;
	auio.uio_segflg = UIO_USERSPACE;
	auio.uio_rw = UIO_READ;
	auio.uio_procp = p;
	auio.uio_offset = 0;			/* XXX */
	auio.uio_resid = 0;
	iov = mp->msg_iov;
	for (i = 0; i < mp->msg_iovlen; i++, iov++) {
		if (iov->iov_len < 0)
			return (EINVAL);
		if ((auio.uio_resid += iov->iov_len) < 0)
			return (EINVAL);
	}
#ifdef KTRACE
	if (KTRPOINT(p, KTR_GENIO)) {
		int iovlen = auio.uio_iovcnt * sizeof (struct iovec);

		MALLOC(ktriov, struct iovec *, iovlen, M_TEMP, M_WAITOK);
		bcopy((caddr_t)auio.uio_iov, (caddr_t)ktriov, iovlen);
	}
#endif
	len = auio.uio_resid;
	if (error = soreceive((struct socket *)fp->f_data, &from, &auio,
	    (struct mbuf **)0, mp->msg_control ? &control : (struct mbuf **)0,
	    &mp->msg_flags)) {
		if (auio.uio_resid != len && (error == ERESTART ||
		    error == EINTR || error == EWOULDBLOCK))
			error = 0;
	}
#ifdef KTRACE
	if (ktriov != NULL) {
		if (error == 0)
			ktrgenio(p->p_tracep, s, UIO_READ,
				ktriov, len - auio.uio_resid, error);
		FREE(ktriov, M_TEMP);
	}
#endif
	if (error)
		goto out;
	*retsize = len - auio.uio_resid;
	if (mp->msg_name) {
		len = mp->msg_namelen;
		if (len <= 0 || from == 0)
			len = 0;
		else {
#ifdef COMPAT_OLDSOCK
			if (mp->msg_flags & MSG_COMPAT)
				mtod(from, struct osockaddr *)->sa_family =
				    mtod(from, struct sockaddr *)->sa_family;
#endif
			if (len > from->m_len)
				len = from->m_len;
			/* else if len < from->m_len ??? */
			if (error = copyout(mtod(from, caddr_t),
			    (caddr_t)mp->msg_name, (unsigned)len))
				goto out;
		}
		mp->msg_namelen = len;
		if (namelenp &&
		    (error = copyout((caddr_t)&len, namelenp, sizeof (int)))) {
#ifdef COMPAT_OLDSOCK
			if (mp->msg_flags & MSG_COMPAT)
				error = 0;	/* old recvfrom didn't check */
			else
#endif
			goto out;
		}
	}
	if (mp->msg_control) {
#ifdef COMPAT_OLDSOCK
		/*
		 * We assume that old recvmsg calls won't receive access
		 * rights and other control info, esp. as control info
		 * is always optional and those options didn't exist in 4.3.
		 * If we receive rights, trim the cmsghdr; anything else
		 * is tossed.
		 */
		if (control && mp->msg_flags & MSG_COMPAT) {
			if (mtod(control, struct cmsghdr *)->cmsg_level !=
			    SOL_SOCKET ||
			    mtod(control, struct cmsghdr *)->cmsg_type !=
			    SCM_RIGHTS) {
				mp->msg_controllen = 0;
				goto out;
			}
			control->m_len -= sizeof (struct cmsghdr);
			control->m_data += sizeof (struct cmsghdr);
		}
#endif
		len = mp->msg_controllen;
		if (len <= 0 || control == 0)
			len = 0;
		else {
			if (len >= control->m_len)
				len = control->m_len;
			else
				mp->msg_flags |= MSG_CTRUNC;
			error = copyout((caddr_t)mtod(control, caddr_t),
			    (caddr_t)mp->msg_control, (unsigned)len);
		}
		mp->msg_controllen = len;
	}
out:
	if (from)
		m_freem(from);
	if (control)
		m_freem(control);
	return (error);
}

/*
	函数功能: 关闭连接的读通道、写通道或读写通道

	内部实现: 本地不再通过socket读写数据并进行协议处理(对于TCP要进行断开连接操作)

	调用举例：
	FREAD：读通道
	FWRITE：写通道
	FREAD | FWRITE：读写通道

	shutdown(fd_s, FREAD)
*/

struct shutdown_args {
	int	s;
	int	how;
};
/* ARGSUSED */
shutdown(p, uap, retval)
	struct proc *p;
	register struct shutdown_args *uap;
	int *retval;
{
	struct file *fp;
	int error;

	if (error = getsock(p->p_fd, uap->s, &fp))
		return (error);
	return (soshutdown((struct socket *)fp->f_data, uap->how));
}

struct setsockopt_args {
	int	s;
	int	level;
	int	name;
	caddr_t	val;
	int	valsize;
};
/* ARGSUSED */
setsockopt(p, uap, retval)
	struct proc *p;
	register struct setsockopt_args *uap;
	int *retval;
{
	struct file *fp;
	struct mbuf *m = NULL;
	int error;

	if (error = getsock(p->p_fd, uap->s, &fp))
		return (error);
	if (uap->valsize > MLEN)
		return (EINVAL);
	if (uap->val) {
		m = m_get(M_WAIT, MT_SOOPTS);
		if (m == NULL)
			return (ENOBUFS);
		if (error = copyin(uap->val, mtod(m, caddr_t),
		    (u_int)uap->valsize)) {
			(void) m_free(m);
			return (error);
		}
		m->m_len = uap->valsize;
	}
	return (sosetopt((struct socket *)fp->f_data, uap->level,
	    uap->name, m));
}

struct getsockopt_args {
	int	s;
	int	level;
	int	name;
	caddr_t	val;
	int	*avalsize;
};
/* ARGSUSED */
getsockopt(p, uap, retval)
	struct proc *p;
	register struct getsockopt_args *uap;
	int *retval;
{
	struct file *fp;
	struct mbuf *m = NULL;
	int valsize, error;

	if (error = getsock(p->p_fd, uap->s, &fp))
		return (error);
	if (uap->val) {
		if (error = copyin((caddr_t)uap->avalsize, (caddr_t)&valsize,
		    sizeof (valsize)))
			return (error);
	} else
		valsize = 0;
	if ((error = sogetopt((struct socket *)fp->f_data, uap->level,
	    uap->name, &m)) == 0 && uap->val && valsize && m != NULL) {
		if (valsize > m->m_len)
			valsize = m->m_len;
		error = copyout(mtod(m, caddr_t), uap->val, (u_int)valsize);
		if (error == 0)
			error = copyout((caddr_t)&valsize,
			    (caddr_t)uap->avalsize, sizeof (valsize));
	}
	if (m != NULL)
		(void) m_free(m);
	return (error);
}

struct pipe_args {
	int	dummy;
};
/* ARGSUSED */
pipe(p, uap, retval)
	struct proc *p;
	struct pipe_args *uap;
	int retval[];
{
	register struct filedesc *fdp = p->p_fd;
	struct file *rf, *wf;
	struct socket *rso, *wso;
	int fd, error;

	if (error = socreate(AF_UNIX, &rso, SOCK_STREAM, 0))
		return (error);
	if (error = socreate(AF_UNIX, &wso, SOCK_STREAM, 0))
		goto free1;
	if (error = falloc(p, &rf, &fd))
		goto free2;
	retval[0] = fd;
	rf->f_flag = FREAD;
	rf->f_type = DTYPE_SOCKET;
	rf->f_ops = &socketops;
	rf->f_data = (caddr_t)rso;
	if (error = falloc(p, &wf, &fd))
		goto free3;
	wf->f_flag = FWRITE;
	wf->f_type = DTYPE_SOCKET;
	wf->f_ops = &socketops;
	wf->f_data = (caddr_t)wso;
	retval[1] = fd;
	if (error = unp_connect2(wso, rso))
		goto free4;
	return (0);
free4:
	ffree(wf);
	fdp->fd_ofiles[retval[1]] = 0;
free3:
	ffree(rf);
	fdp->fd_ofiles[retval[0]] = 0;
free2:
	(void)soclose(wso);
free1:
	(void)soclose(rso);
	return (error);
}

/*
 * Get socket name.
 */
struct getsockname_args {
	int	fdes;
	caddr_t	asa;
	int	*alen;
#ifdef COMPAT_OLDSOCK
	int	compat_43;	/* pseudo */
#endif
};
#ifdef COMPAT_OLDSOCK
getsockname(p, uap, retval)
	struct proc *p;
	struct getsockname_args *uap;
	int *retval;
{

	uap->compat_43 = 0;
	return (getsockname1(p, uap, retval));
}

ogetsockname(p, uap, retval)
	struct proc *p;
	struct getsockname_args *uap;
	int *retval;
{

	uap->compat_43 = 1;
	return (getsockname1(p, uap, retval));
}
#else /* COMPAT_OLDSOCK */

#define	getsockname1	getsockname
#endif

/* ARGSUSED */
getsockname1(p, uap, retval)
	struct proc *p;
	register struct getsockname_args *uap;
	int *retval;
{
	struct file *fp;
	register struct socket *so;
	struct mbuf *m;
	int len, error;

	if (error = getsock(p->p_fd, uap->fdes, &fp))
		return (error);
	if (error = copyin((caddr_t)uap->alen, (caddr_t)&len, sizeof (len)))
		return (error);
	so = (struct socket *)fp->f_data;
	m = m_getclr(M_WAIT, MT_SONAME);
	if (m == NULL)
		return (ENOBUFS);
	if (error = (*so->so_proto->pr_usrreq)(so, PRU_SOCKADDR, 0, m, 0))
		goto bad;
	if (len > m->m_len)
		len = m->m_len;
#ifdef COMPAT_OLDSOCK
	if (uap->compat_43)
		mtod(m, struct osockaddr *)->sa_family =
		    mtod(m, struct sockaddr *)->sa_family;
#endif
	error = copyout(mtod(m, caddr_t), (caddr_t)uap->asa, (u_int)len);
	if (error == 0)
		error = copyout((caddr_t)&len, (caddr_t)uap->alen,
		    sizeof (len));
bad:
	m_freem(m);
	return (error);
}

/*
 * Get name of peer for connected socket.
 */
struct getpeername_args {
	int	fdes;
	caddr_t	asa;
	int	*alen;
#ifdef COMPAT_OLDSOCK
	int	compat_43;	/* pseudo */
#endif
};

#ifdef COMPAT_OLDSOCK
getpeername(p, uap, retval)
	struct proc *p;
	struct getpeername_args *uap;
	int *retval;
{

	uap->compat_43 = 0;
	return (getpeername1(p, uap, retval));
}

ogetpeername(p, uap, retval)
	struct proc *p;
	struct getpeername_args *uap;
	int *retval;
{

	uap->compat_43 = 1;
	return (getpeername1(p, uap, retval));
}
#else /* COMPAT_OLDSOCK */

#define	getpeername1	getpeername
#endif

/* ARGSUSED */
getpeername1(p, uap, retval)
	struct proc *p;
	register struct getpeername_args *uap;
	int *retval;
{
	struct file *fp;
	register struct socket *so;
	struct mbuf *m;
	int len, error;

	if (error = getsock(p->p_fd, uap->fdes, &fp))
		return (error);
	so = (struct socket *)fp->f_data;
	if ((so->so_state & (SS_ISCONNECTED|SS_ISCONFIRMING)) == 0)
		return (ENOTCONN);
	if (error = copyin((caddr_t)uap->alen, (caddr_t)&len, sizeof (len)))
		return (error);
	m = m_getclr(M_WAIT, MT_SONAME);
	if (m == NULL)
		return (ENOBUFS);
	if (error = (*so->so_proto->pr_usrreq)(so, PRU_PEERADDR, 0, m, 0))
		goto bad;
	if (len > m->m_len)
		len = m->m_len;
#ifdef COMPAT_OLDSOCK
	if (uap->compat_43)
		mtod(m, struct osockaddr *)->sa_family =
		    mtod(m, struct sockaddr *)->sa_family;
#endif
	if (error = copyout(mtod(m, caddr_t), (caddr_t)uap->asa, (u_int)len))
		goto bad;
	error = copyout((caddr_t)&len, (caddr_t)uap->alen, sizeof (len));
bad:
	m_freem(m);
	return (error);
}

/* 把进程传来的buf信息，拷贝(copyin函数)到内核mbuf中 */
sockargs(mp, buf, buflen, type)
	struct mbuf **mp;
	caddr_t buf;
	int buflen, type;
{
	register struct sockaddr *sa;
	register struct mbuf *m;
	int error;

	if ((u_int)buflen > MLEN) {
#ifdef COMPAT_OLDSOCK
		if (type == MT_SONAME && (u_int)buflen <= 112)
			buflen = MLEN;		/* unix domain compat. hack */
		else
#endif
		return (EINVAL);
	}
	m = m_get(M_WAIT, type);
	if (m == NULL)
		return (ENOBUFS);
	m->m_len = buflen;
	error = copyin(buf, mtod(m, caddr_t), (u_int)buflen);
	if (error)
		(void) m_free(m);
	else {
		*mp = m;
		if (type == MT_SONAME) {				/* 如果type是MT_SONAME，说明传入的buf是一个sockaddr结构 */
			sa = mtod(m, struct sockaddr *);

#if defined(COMPAT_OLDSOCK) && BYTE_ORDER != BIG_ENDIAN
			if (sa->sa_family == 0 && sa->sa_len < AF_MAX)
				sa->sa_family = sa->sa_len;
#endif
			sa->sa_len = buflen;
		}
	}
	return (error);
}

/* 根据socket 文件描述符从进程文件描述符表中，找到socket 文件描述符结构 */
getsock(fdp, fdes, fpp)
	struct filedesc *fdp;
	int fdes;
	struct file **fpp;
{
	register struct file *fp;

	if ((unsigned)fdes >= fdp->fd_nfiles ||
	    (fp = fdp->fd_ofiles[fdes]) == NULL)
		return (EBADF);
	if (fp->f_type != DTYPE_SOCKET)
		return (ENOTSOCK);
	*fpp = fp;
	return (0);
}
